1. Field of the Invention
The present invention relates generally to a rotation balance control mechanism controlling a rotation balance of a rotary head drum apparatus, and more particularly, to a rotary head drum apparatus rotation balance control mechanism capable of effectively controlling the balance of the rotary head drum apparatus at high rotation speeds.
2. Description of the Related Art
A rotary head drum apparatus comprising a fixed drum and a rotary drum is built into a variety of types of electronic recording/reproducing equipment, including for example a videocassette tape recorder (VCR) or digital audio tape recorder (DAT). Such a rotary head drum apparatus requires that the magnetic tape that functions as the recording medium be wound helically around the rotary head drum, so the rotary head drum is mounted on a main chassis in an inclined or tilted state, that is, at an angle to the surface of the chassis.
Conventionally, as a method for adjusting or controlling the rotation balance of the tilted rotary drum of such a rotary head drum apparatus, the mounting of a balance weight for adjusting the balance of the rotary drum is known.
However, although the rotation speed of the rotary drum has conventionally been approximately 4,000 rpm, a growing the need to increase the speed with which data is transferred to and from the magnetic tape now requires rotation speeds of approximately 12,000 rpm. At such high rotation speeds the rotary drum begins to oscillate, causing the track of the head to wobble and adversely affecting the apparatus itself as well as the magnetic tape. The conventional balance control method is inadequate at such high rotation speeds of the rotary drum.
Accordingly, it is a general object of the present invention to provide an improved and useful rotation balance control mechanism controlling a rotation balance of a rotary head, in which the disadvantages described above are eliminated.
The above-described object of the present invention is achieved by a rotation balance control mechanism controlling a rotation balance of a rotary head drum apparatus comprising a fixed drum and a rotary drum and a drum motor unit urging the rotary drum, the rotation balance control mechanism comprising a rotor plate mounted on a shaft mount of the drum motor, the rotor plate capable of mounting a balance weight for controlling the rotation balance of the rotary head drum apparatus.
According to the invention described above, oscillation generated by the high speed of rotation of the rotary drum can be effectively reduced, thereby stabilizing the track of the head and reducing the adverse effects of poor head tracking on the apparatus itself as well as on the magnetic tape.
Additionally, the above-described object of the present invention is also achieved by the rotation balance control mechanism as described above, wherein:
a solder mount formed from solderable material is provided on at least one surface of the rotor plate; and
soldering is formed as a balance weight on the solder mount.
According to the invention described above, the balance weight does not fly off at high rotation speeds.
Additionally, the above-described object of the present invention is also achieved by the rotation balance control mechanism as described above, wherein the solder mount comprises a plurality of solder portions arranged in concentric offset circles around a center point of the rotor plate.
According to the invention described above, the shape of the solder portions is not set but may be of a variety of shapes, including, for example, triangular or circular shapes. Additionally, provided that all such solder portions are of a predetermined shape and are spaced a predetermined distance apart, their positions may be changed in a radial direction. Additionally, the effect of the present invention may still be achieved even if the solder portions have a random shape, size and position.
As a result, it is possible to mount a balance weight of a preferred weight at a preferred position in both a direction of a radius of the rotor plate and a periphery of the rotor plate, thereby making rotational balance adjustment easy and accurate.
Additionally, the above-described object of the present invention is also achieved by the rotation balance control mechanism as described above, wherein the rotor plate is made of silicon steel.
According to the invention described above, iron loss caused by eddy-current loss as well as hysteresis loss can be reduced. Additionally, in place of the silicon steel plate a zinc-plated steel plate may be used instead, thus providing easy and accurate soldering. Additionally, in place of the silicon steel plate an ordinary steel plate may be used instead, thus reducing the cost of manufacture.
Additionally, the above-described object of the present invention is also achieved by the rotation balance control mechanism as described above, wherein the rotor plate comprises a two-layer structure, a first layer comprising a silicon steel plate on a side opposite a stator substrate of the drum motor, a second layer comprising an insulating material adjoining a back surface of the first layer, the solder mount being formed on the back surface of the first layer.
According to the invention described above, it is possible to provide a secure electromagnetic shield and at the same time securely form the solder mount capable of providing rotation balance control with ease and thus achieve the effects of the present invention. Additionally, forming the individual solder portions a predetermined distance apart interferes with heat transmission to an outer periphery of the rotor plate, thus reducing heat dissipation. It should be noted that in place of the silicon steel plate either a zinc-plated steel plate or an ordinary steel plate may be used instead.